Allow asynchronous deferral in NavigationSimulator

content/browser/frame_host/navigation_handle_impl.h

Index: content/browser/frame_host/navigation_handle_impl.h
diff --git a/content/browser/frame_host/navigation_handle_impl.h b/content/browser/frame_host/navigation_handle_impl.h
index 275c66750a3377e0bb4aa72cda6c2fa841bd08f4..853c2fbd2ff85b0f3492ef653388c133ce030fa7 100644
--- a/content/browser/frame_host/navigation_handle_impl.h
+++ b/content/browser/frame_host/navigation_handle_impl.h
@@ -346,6 +346,11 @@ class CONTENT_EXPORT NavigationHandleImpl : public NavigationHandle {
     response_headers_ = response_headers;
   }
 
+  void set_complete_callback_for_testing(
+      const ThrottleChecksFinishedCallback& callback) {
+    complete_callback_for_testing_ = callback;
+  }
+
  private:
   friend class NavigationHandleImplTest;
 
@@ -447,9 +452,16 @@ class CONTENT_EXPORT NavigationHandleImpl : public NavigationHandle {
   // The mixed content context type for potential mixed content checks.
   blink::WebMixedContentContextType mixed_content_context_type_;
 
-  // This callback will be run when all throttle checks have been performed.
+  // This callback will be run when all throttle checks have been performed. Be
+  // careful about relying on it as the member may be removed as part of the
+  // PlzNavigate refactoring.
   ThrottleChecksFinishedCallback complete_callback_;
 
+  // This test-only callback will be run when all throttle checks have been
+  // performed.
+  // TODO(clamy): Revisit the unit test architecture when PlzNavigate ships.
+  ThrottleChecksFinishedCallback complete_callback_for_testing_;
+
   // PlzNavigate
   // Manages the lifetime of a pre-created ServiceWorkerProviderHost until a
   // corresponding ServiceWorkerNetworkProvider is created in the renderer.